Not an unusual thing to occour.
Holding the neck in the playing position, turning the adjusting nut clockwise should loosen the truss then the double action truss rod should start to pull the neck forwards.
If this isnt happening there may be a burr on the thread that is fouling the doings up or you just have a rather tight truss rod..

Try clamping the neck (at the heel) onto your workbench then gently push the headstock end down whilst turning the adjusting nut.
By doing this you are taking the pressure off the nut and it may just turn more easily.
Hope this helps, keep us posted!